3,605 research outputs found
Status of the KTeV Experiment at Fermilab
The KTeV experiment is a fixed target experiment at Fermilab. Its primary
goal is the search for direct CP violation in the decay of neutral kaons. Its
current status and some preliminary results will be discussed.Comment: 5 pages Latex, 4 figures; to be published in the proceedings of the
XVI International Workshop on Weak Interactions and Neutrinos, WIN '97,
Capri, Italy, June 22-28, 199
Angular Distribution and CP Asymmetries in the Decays B->K^-pi^+e^-e^+ and B->pi^-pi^+e^-e^+
The short-distance Hamiltonian describing b->s(d)e^-e^+ in the standard model
is used to obtain the decay spectrum of \bar{B}->K^-pi^+e^-e^+ and
\bar{B}->pi^-pi^+e^-e^+, assuming the Kpi and pipi systems to be the decay
products of K^* and rho respectively. Specific features calculated are (i)
angular distribution of K^- (or pi^-) in the K^-pi^+ (or pi^-pi^+)
centre-of-mass (c.m.) frame; (ii) angular distribution of e^- in the e^-e^+
c.m. frame; and (iii) the correlation between the meson and lepton planes. We
also derive CP-violating observables obtained by combining the above decays
with the conjugate processes B->K^+pi^-e^-e^+ and B->pi^-pi^+e^-e^+.Comment: 19 pages, REVTeX, no figures. Equations (2.19a), (2.19b), (5.5)-(5.7)
have been corrected; all results remain unchanged. These changes will appear
in an Erratum submitted to Phys. Rev.
CP Violation and Arrows of Time Evolution of a Neutral or Meson from an Incoherent to a Coherent State
We study the evolution of a neutral meson prepared as an incoherent equal
mixture of and . Denoting the density matrix by \rho(t) =
{1/2} N(t) [\1 + \vec{\zeta}(t) \cdot \vec{\sigma} ] , the norm of the state
is found to decrease monotonically from one to zero, while the magnitude
of the Stokes vector increases monotonically from zero to
one. This property qualifies these observables as arrows of time. Requiring
monotonic behaviour of for arbitrary values of and
yields a bound on the CP-violating overlap , which is similar to, but weaker than, the known unitarity
bound. A similar requirement on yields a new bound,
which is particularly effective in limiting
the CP-violating overlap in the - system. We obtain the Stokes
parameter which shows how the average strangeness of the beam
evolves from zero to . The evolution of the Stokes vector from
to has a resemblance to an order
parameter of a system undergoing spontaneous symmetry breaking.Comment: 13 pages, 6 figures. Inserted conon "." in title; minor change in
text. To appear in Physical review
Baryon Magnetic Moments and Proton Spin: A Model with Collective Quark Rotation
We analyse the baryon magnetic moments in a model that relates them to the
parton spins , , , and includes a contribution
from orbital angular momentum. The specific assumption is the existence of a
3-quark correlation (such as a flux string) that rotates with angular momentum
around the proton spin axis. A fit to the baryon magnetic
moments, constrained by the measured values of the axial vector coupling
constants , , yields , , where the error is a theoretical
estimate. A second fit, under slightly different assumptions, gives , with no constraint on . The
model provides a consistent description of axial vector couplings, magnetic
moments and the quark polarization measured in deep
inelastic scattering. The fits suggest that a significant part of the angular
momentum of the proton may reside in a collective rotation of the constituent
quarks.Comment: 16 pages, 3 ps-figures, uses RevTeX. Abstract, Sec. II, III and IV
have been expande
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